In a typical LCD device or an OLED device, each point (pixel) has its colour shown in the form of a mixed light by a plurality of subpixels. For instance, each pixel is composed of a red subpixel, a green subpixel and a blue subpixel (RGB mode).
To improve visual effects, people set higher and higher requirements for resolution (the number of pixels per unit of measurement) of display devices. The size of subpixels is required to be smaller, but cannot be reduced infinitely due to the process limitations.